[lttng-tools.git] / src / bin / lttng-relayd / live.c

/*
 * Copyright (C) 2013 - Julien Desfossez <jdesfossez@efficios.com>
 *                      David Goulet <dgoulet@efficios.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#define _GNU_SOURCE
#include <getopt.h>
#include <grp.h>
#include <limits.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <inttypes.h>
#include <urcu/futex.h>
#include <urcu/uatomic.h>
#include <unistd.h>
#include <fcntl.h>
#include <config.h>

#include <lttng/lttng.h>
#include <common/common.h>
#include <common/compat/poll.h>
#include <common/compat/socket.h>
#include <common/compat/endian.h>
#include <common/defaults.h>
#include <common/futex.h>
#include <common/index/index.h>
#include <common/sessiond-comm/sessiond-comm.h>
#include <common/sessiond-comm/inet.h>
#include <common/sessiond-comm/relayd.h>
#include <common/uri.h>
#include <common/utils.h>

#include "cmd.h"
#include "live.h"
#include "lttng-relayd.h"
#include "utils.h"
#include "health-relayd.h"
#include "testpoint.h"
#include "viewer-stream.h"
#include "stream.h"
#include "session.h"
#include "ctf-trace.h"
#include "connection.h"

static struct lttng_uri *live_uri;

/*
 * This pipe is used to inform the worker thread that a command is queued and
 * ready to be processed.
 */
static int live_conn_pipe[2] = { -1, -1 };

/* Shared between threads */
static int live_dispatch_thread_exit;

static pthread_t live_listener_thread;
static pthread_t live_dispatcher_thread;
static pthread_t live_worker_thread;

/*
 * Relay command queue.
 *
 * The live_thread_listener and live_thread_dispatcher communicate with this
 * queue.
 */
static struct relay_conn_queue viewer_conn_queue;

static uint64_t last_relay_viewer_session_id;

/*
 * Cleanup the daemon
 */
static
void cleanup(void)
{
        DBG("Cleaning up");

        free(live_uri);
}

/*
 * Receive a request buffer using a given socket, destination allocated buffer
 * of length size.
 *
 * Return the size of the received message or else a negative value on error
 * with errno being set by recvmsg() syscall.
 */
static
ssize_t recv_request(struct lttcomm_sock *sock, void *buf, size_t size)
{
        ssize_t ret;

        assert(sock);
        assert(buf);

        ret = sock->ops->recvmsg(sock, buf, size, 0);
        if (ret < 0 || ret != size) {
                if (ret == 0) {
                        /* Orderly shutdown. Not necessary to print an error. */
                        DBG("Socket %d did an orderly shutdown", sock->fd);
                } else {
                        ERR("Relay failed to receive request.");
                }
                ret = -1;
        }

        return ret;
}

/*
 * Send a response buffer using a given socket, source allocated buffer of
 * length size.
 *
 * Return the size of the sent message or else a negative value on error with
 * errno being set by sendmsg() syscall.
 */
static
ssize_t send_response(struct lttcomm_sock *sock, void *buf, size_t size)
{
        ssize_t ret;

        assert(sock);
        assert(buf);

        ret = sock->ops->sendmsg(sock, buf, size, 0);
        if (ret < 0) {
                ERR("Relayd failed to send response.");
        }

        return ret;
}

/*
 * Atomically check if new streams got added in one of the sessions attached
 * and reset the flag to 0.
 *
 * Returns 1 if new streams got added, 0 if nothing changed, a negative value
 * on error.
 */
static
int check_new_streams(struct relay_connection *conn)
{
        struct relay_session *session;
        unsigned long current_val;
        int ret = 0;

        if (!conn->viewer_session) {
                goto end;
        }
        cds_list_for_each_entry(session,
                        &conn->viewer_session->sessions_head,
                        viewer_session_list) {
                current_val = uatomic_cmpxchg(&session->new_streams, 1, 0);
                ret = current_val;
                if (ret == 1) {
                        goto end;
                }
        }

end:
        return ret;
}

/*
 * Send viewer streams to the given socket. The ignore_sent_flag indicates if
 * this function should ignore the sent flag or not.
 *
 * Return 0 on success or else a negative value.
 */
static
ssize_t send_viewer_streams(struct lttcomm_sock *sock,
                struct relay_session *session, unsigned int ignore_sent_flag)
{
        ssize_t ret;
        struct lttng_viewer_stream send_stream;
        struct lttng_ht_iter iter;
        struct relay_viewer_stream *vstream;

        assert(session);

        rcu_read_lock();

        cds_lfht_for_each_entry(viewer_streams_ht->ht, &iter.iter, vstream,
                        stream_n.node) {
                struct ctf_trace *ctf_trace;

                health_code_update();

                /* Ignore if not the same session. */
                if (vstream->session_id != session->id ||
                                (!ignore_sent_flag && vstream->sent_flag)) {
                        continue;
                }

                ctf_trace = ctf_trace_find_by_path(session->ctf_traces_ht,
                                vstream->path_name);
                assert(ctf_trace);

                send_stream.id = htobe64(vstream->stream_handle);
                send_stream.ctf_trace_id = htobe64(ctf_trace->id);
                send_stream.metadata_flag = htobe32(vstream->metadata_flag);
                strncpy(send_stream.path_name, vstream->path_name,
                                sizeof(send_stream.path_name));
                strncpy(send_stream.channel_name, vstream->channel_name,
                                sizeof(send_stream.channel_name));

                DBG("Sending stream %" PRIu64 " to viewer", vstream->stream_handle);
                ret = send_response(sock, &send_stream, sizeof(send_stream));
                if (ret < 0) {
                        goto end_unlock;
                }
                vstream->sent_flag = 1;
        }

        ret = 0;

end_unlock:
        rcu_read_unlock();
        return ret;
}

/*
 * Create every viewer stream possible for the given session with the seek
 * type. Three counters *can* be return which are in order the total amount of
 * viewer stream of the session, the number of unsent stream and the number of
 * stream created. Those counters can be NULL and thus will be ignored.
 *
 * Return 0 on success or else a negative value.
 */
static
int make_viewer_streams(struct relay_session *session,
                enum lttng_viewer_seek seek_t, uint32_t *nb_total, uint32_t *nb_unsent,
                uint32_t *nb_created)
{
        int ret;
        struct lttng_ht_iter iter;
        struct ctf_trace *ctf_trace;

        assert(session);

        /*
         * This is to make sure we create viewer streams for a full received
         * channel. For instance, if we have 8 streams for a channel that are
         * concurrently being flagged ready, we can end up creating just a subset
         * of the 8 streams (the ones that are flagged). This lock avoids this
         * limbo state.
         */
        pthread_mutex_lock(&session->viewer_ready_lock);

        /*
         * Create viewer streams for relay streams that are ready to be used for a
         * the given session id only.
         */
        rcu_read_lock();
        cds_lfht_for_each_entry(session->ctf_traces_ht->ht, &iter.iter, ctf_trace,
                        node.node) {
                struct relay_stream *stream;

                health_code_update();

                if (ctf_trace->invalid_flag) {
                        continue;
                }

                cds_list_for_each_entry(stream, &ctf_trace->stream_list, trace_list) {
                        struct relay_viewer_stream *vstream;

                        if (!stream->viewer_ready) {
                                continue;
                        }

                        vstream = viewer_stream_find_by_id(stream->stream_handle);
                        if (!vstream) {
                                vstream = viewer_stream_create(stream, seek_t, ctf_trace);
                                if (!vstream) {
                                        ret = -1;
                                        goto error_unlock;
                                }
                                /* Acquire reference to ctf_trace. */
                                ctf_trace_get_ref(ctf_trace);

                                if (nb_created) {
                                        /* Update number of created stream counter. */
                                        (*nb_created)++;
                                }
                        } else if (!vstream->sent_flag && nb_unsent) {
                                /* Update number of unsent stream counter. */
                                (*nb_unsent)++;
                        }
                        /* Update number of total stream counter. */
                        if (nb_total) {
                                (*nb_total)++;
                        }
                }
        }

        ret = 0;

error_unlock:
        rcu_read_unlock();
        pthread_mutex_unlock(&session->viewer_ready_lock);
        return ret;
}

/*
 * Write to writable pipe used to notify a thread.
 */
static
int notify_thread_pipe(int wpipe)
{
        ssize_t ret;

        ret = lttng_write(wpipe, "!", 1);
        if (ret < 1) {
                PERROR("write poll pipe");
        }

        return (int) ret;
}

/*
 * Stop all threads by closing the thread quit pipe.
 */
static
void stop_threads(void)
{
        int ret;

        /* Stopping all threads */
        DBG("Terminating all live threads");
        ret = notify_thread_pipe(thread_quit_pipe[1]);
        if (ret < 0) {
                ERR("write error on thread quit pipe");
        }

        /* Dispatch thread */
        CMM_STORE_SHARED(live_dispatch_thread_exit, 1);
        futex_nto1_wake(&viewer_conn_queue.futex);
}

/*
 * Create a poll set with O_CLOEXEC and add the thread quit pipe to the set.
 */
static
int create_thread_poll_set(struct lttng_poll_event *events, int size)
{
        int ret;

        if (events == NULL || size == 0) {
                ret = -1;
                goto error;
        }

        ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
        if (ret < 0) {
                goto error;
        }

        /* Add quit pipe */
        ret = lttng_poll_add(events, thread_quit_pipe[0], LPOLLIN | LPOLLERR);
        if (ret < 0) {
                goto error;
        }

        return 0;

error:
        return ret;
}

/*
 * Check if the thread quit pipe was triggered.
 *
 * Return 1 if it was triggered else 0;
 */
static
int check_thread_quit_pipe(int fd, uint32_t events)
{
        if (fd == thread_quit_pipe[0] && (events & LPOLLIN)) {
                return 1;
        }

        return 0;
}

/*
 * Create and init socket from uri.
 */
static
struct lttcomm_sock *init_socket(struct lttng_uri *uri)
{
        int ret;
        struct lttcomm_sock *sock = NULL;

        sock = lttcomm_alloc_sock_from_uri(uri);
        if (sock == NULL) {
                ERR("Allocating socket");
                goto error;
        }

        ret = lttcomm_create_sock(sock);
        if (ret < 0) {
                goto error;
        }
        DBG("Listening on sock %d for live", sock->fd);

        ret = sock->ops->bind(sock);
        if (ret < 0) {
                goto error;
        }

        ret = sock->ops->listen(sock, -1);
        if (ret < 0) {
                goto error;

        }

        return sock;

error:
        if (sock) {
                lttcomm_destroy_sock(sock);
        }
        return NULL;
}

/*
 * This thread manages the listening for new connections on the network
 */
static
void *thread_listener(void *data)
{
        int i, ret, pollfd, err = -1;
        uint32_t revents, nb_fd;
        struct lttng_poll_event events;
        struct lttcomm_sock *live_control_sock;

        DBG("[thread] Relay live listener started");

        health_register(health_relayd, HEALTH_RELAYD_TYPE_LIVE_LISTENER);

        health_code_update();

        live_control_sock = init_socket(live_uri);
        if (!live_control_sock) {
                goto error_sock_control;
        }

        /* Pass 2 as size here for the thread quit pipe and control sockets. */
        ret = create_thread_poll_set(&events, 2);
        if (ret < 0) {
                goto error_create_poll;
        }

        /* Add the control socket */
        ret = lttng_poll_add(&events, live_control_sock->fd, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error_poll_add;
        }

        lttng_relay_notify_ready();

        if (testpoint(relayd_thread_live_listener)) {
                goto error_testpoint;
        }

        while (1) {
                health_code_update();

                DBG("Listener accepting live viewers connections");

restart:
                health_poll_entry();
                ret = lttng_poll_wait(&events, -1);
                health_poll_exit();
                if (ret < 0) {
                        /*
                         * Restart interrupted system call.
                         */
                        if (errno == EINTR) {
                                goto restart;
                        }
                        goto error;
                }
                nb_fd = ret;

                DBG("Relay new viewer connection received");
                for (i = 0; i < nb_fd; i++) {
                        health_code_update();

                        /* Fetch once the poll data */
                        revents = LTTNG_POLL_GETEV(&events, i);
                        pollfd = LTTNG_POLL_GETFD(&events, i);

                        if (!revents) {
                                /* No activity for this FD (poll implementation). */
                                continue;
                        }

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                err = 0;
                                goto exit;
                        }

                        if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                ERR("socket poll error");
                                goto error;
                        } else if (revents & LPOLLIN) {
                                /*
                                 * Get allocated in this thread, enqueued to a global queue,
                                 * dequeued and freed in the worker thread.
                                 */
                                int val = 1;
                                struct relay_connection *new_conn;
                                struct lttcomm_sock *newsock;

                                new_conn = connection_create();
                                if (!new_conn) {
                                        goto error;
                                }

                                newsock = live_control_sock->ops->accept(live_control_sock);
                                if (!newsock) {
                                        PERROR("accepting control sock");
                                        connection_free(new_conn);
                                        goto error;
                                }
                                DBG("Relay viewer connection accepted socket %d", newsock->fd);

                                ret = setsockopt(newsock->fd, SOL_SOCKET, SO_REUSEADDR, &val,
                                                sizeof(val));
                                if (ret < 0) {
                                        PERROR("setsockopt inet");
                                        lttcomm_destroy_sock(newsock);
                                        connection_free(new_conn);
                                        goto error;
                                }
                                new_conn->sock = newsock;

                                /* Enqueue request for the dispatcher thread. */
                                cds_wfcq_enqueue(&viewer_conn_queue.head, &viewer_conn_queue.tail,
                                                 &new_conn->qnode);

                                /*
                                 * Wake the dispatch queue futex. Implicit memory barrier with
                                 * the exchange in cds_wfcq_enqueue.
                                 */
                                futex_nto1_wake(&viewer_conn_queue.futex);
                        }
                }
        }

exit:
error:
error_poll_add:
error_testpoint:
        lttng_poll_clean(&events);
error_create_poll:
        if (live_control_sock->fd >= 0) {
                ret = live_control_sock->ops->close(live_control_sock);
                if (ret) {
                        PERROR("close");
                }
        }
        lttcomm_destroy_sock(live_control_sock);
error_sock_control:
        if (err) {
                health_error();
                DBG("Live viewer listener thread exited with error");
        }
        health_unregister(health_relayd);
        DBG("Live viewer listener thread cleanup complete");
        stop_threads();
        return NULL;
}

/*
 * This thread manages the dispatching of the requests to worker threads
 */
static
void *thread_dispatcher(void *data)
{
        int err = -1;
        ssize_t ret;
        struct cds_wfcq_node *node;
        struct relay_connection *conn = NULL;

        DBG("[thread] Live viewer relay dispatcher started");

        health_register(health_relayd, HEALTH_RELAYD_TYPE_LIVE_DISPATCHER);

        if (testpoint(relayd_thread_live_dispatcher)) {
                goto error_testpoint;
        }

        health_code_update();

        while (!CMM_LOAD_SHARED(live_dispatch_thread_exit)) {
                health_code_update();

                /* Atomically prepare the queue futex */
                futex_nto1_prepare(&viewer_conn_queue.futex);

                do {
                        health_code_update();

                        /* Dequeue commands */
                        node = cds_wfcq_dequeue_blocking(&viewer_conn_queue.head,
                                                         &viewer_conn_queue.tail);
                        if (node == NULL) {
                                DBG("Woken up but nothing in the live-viewer "
                                                "relay command queue");
                                /* Continue thread execution */
                                break;
                        }
                        conn = caa_container_of(node, struct relay_connection, qnode);
                        DBG("Dispatching viewer request waiting on sock %d",
                                        conn->sock->fd);

                        /*
                         * Inform worker thread of the new request. This call is blocking
                         * so we can be assured that the data will be read at some point in
                         * time or wait to the end of the world :)
                         */
                        ret = lttng_write(live_conn_pipe[1], &conn, sizeof(conn));
                        if (ret < 0) {
                                PERROR("write conn pipe");
                                connection_destroy(conn);
                                goto error;
                        }
                } while (node != NULL);

                /* Futex wait on queue. Blocking call on futex() */
                health_poll_entry();
                futex_nto1_wait(&viewer_conn_queue.futex);
                health_poll_exit();
        }

        /* Normal exit, no error */
        err = 0;

error:
error_testpoint:
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }
        health_unregister(health_relayd);
        DBG("Live viewer dispatch thread dying");
        stop_threads();
        return NULL;
}

/*
 * Establish connection with the viewer and check the versions.
 *
 * Return 0 on success or else negative value.
 */
static
int viewer_connect(struct relay_connection *conn)
{
        int ret;
        struct lttng_viewer_connect reply, msg;

        assert(conn);

        conn->version_check_done = 1;

        health_code_update();

        DBG("Viewer is establishing a connection to the relayd.");

        ret = recv_request(conn->sock, &msg, sizeof(msg));
        if (ret < 0) {
                goto end;
        }

        health_code_update();

        memset(&reply, 0, sizeof(reply));
        reply.major = RELAYD_VERSION_COMM_MAJOR;
        reply.minor = RELAYD_VERSION_COMM_MINOR;

        /* Major versions must be the same */
        if (reply.major != be32toh(msg.major)) {
                DBG("Incompatible major versions ([relayd] %u vs [client] %u)",
                                reply.major, be32toh(msg.major));
                ret = -1;
                goto end;
        }

        conn->major = reply.major;
        /* We adapt to the lowest compatible version */
        if (reply.minor <= be32toh(msg.minor)) {
                conn->minor = reply.minor;
        } else {
                conn->minor = be32toh(msg.minor);
        }

        if (be32toh(msg.type) == LTTNG_VIEWER_CLIENT_COMMAND) {
                conn->type = RELAY_VIEWER_COMMAND;
        } else if (be32toh(msg.type) == LTTNG_VIEWER_CLIENT_NOTIFICATION) {
                conn->type = RELAY_VIEWER_NOTIFICATION;
        } else {
                ERR("Unknown connection type : %u", be32toh(msg.type));
                ret = -1;
                goto end;
        }

        reply.major = htobe32(reply.major);
        reply.minor = htobe32(reply.minor);
        if (conn->type == RELAY_VIEWER_COMMAND) {
                /*
                 * Increment outside of htobe64 macro, because can be used more than once
                 * within the macro, and thus the operation may be undefined.
                 */
                last_relay_viewer_session_id++;
                reply.viewer_session_id = htobe64(last_relay_viewer_session_id);
        }

        health_code_update();

        ret = send_response(conn->sock, &reply, sizeof(reply));
        if (ret < 0) {
                goto end;
        }

        health_code_update();

        DBG("Version check done using protocol %u.%u", conn->major, conn->minor);
        ret = 0;

end:
        return ret;
}

/*
 * Send the viewer the list of current sessions.
 *
 * Return 0 on success or else a negative value.
 */
static
int viewer_list_sessions(struct relay_connection *conn)
{
        int ret;
        struct lttng_viewer_list_sessions session_list;
        unsigned long count;
        long approx_before, approx_after;
        struct lttng_ht_iter iter;
        struct lttng_viewer_session send_session;
        struct relay_session *session;

        DBG("List sessions received");

        rcu_read_lock();
        cds_lfht_count_nodes(conn->sessions_ht->ht, &approx_before, &count,
                        &approx_after);
        session_list.sessions_count = htobe32(count);

        health_code_update();

        ret = send_response(conn->sock, &session_list, sizeof(session_list));
        if (ret < 0) {
                goto end_unlock;
        }

        health_code_update();

        cds_lfht_for_each_entry(conn->sessions_ht->ht, &iter.iter, session,
                        session_n.node) {
                health_code_update();

                strncpy(send_session.session_name, session->session_name,
                                sizeof(send_session.session_name));
                strncpy(send_session.hostname, session->hostname,
                                sizeof(send_session.hostname));
                send_session.id = htobe64(session->id);
                send_session.live_timer = htobe32(session->live_timer);
                send_session.clients = htobe32(session->viewer_refcount);
                send_session.streams = htobe32(session->stream_count);

                health_code_update();

                ret = send_response(conn->sock, &send_session, sizeof(send_session));
                if (ret < 0) {
                        goto end_unlock;
                }
        }
        health_code_update();

        rcu_read_unlock();
        ret = 0;
        goto end;

end_unlock:
        rcu_read_unlock();

end:
        return ret;
}

/*
 * Check if a connection is attached to a session.
 * Return 1 if attached, 0 if not attached, a negative value on error.
 */
static
int session_attached(struct relay_connection *conn, uint64_t session_id)
{
        struct relay_session *session;
        int found = 0;

        if (!conn->viewer_session) {
                goto end;
        }
        cds_list_for_each_entry(session,
                        &conn->viewer_session->sessions_head,
                        viewer_session_list) {
                if (session->id == session_id) {
                        found = 1;
                        goto end;
                }
        }

end:
        return found;
}

/*
 * Delete all streams for a specific session ID.
 */
static void destroy_viewer_streams_by_session(struct relay_session *session)
{
        struct relay_viewer_stream *stream;
        struct lttng_ht_iter iter;

        assert(session);

        rcu_read_lock();
        cds_lfht_for_each_entry(viewer_streams_ht->ht, &iter.iter, stream,
                        stream_n.node) {
                struct ctf_trace *ctf_trace;

                health_code_update();
                if (stream->session_id != session->id) {
                        continue;
                }

                ctf_trace = ctf_trace_find_by_path(session->ctf_traces_ht,
                                stream->path_name);
                assert(ctf_trace);

                viewer_stream_delete(stream);

                if (stream->metadata_flag) {
                        ctf_trace->metadata_sent = 0;
                        ctf_trace->viewer_metadata_stream = NULL;
                }

                viewer_stream_destroy(ctf_trace, stream);
        }
        rcu_read_unlock();
}

static void try_destroy_streams(struct relay_session *session)
{
        struct ctf_trace *ctf_trace;
        struct lttng_ht_iter iter;

        assert(session);

        cds_lfht_for_each_entry(session->ctf_traces_ht->ht, &iter.iter, ctf_trace,
                        node.node) {
                /* Attempt to destroy the ctf trace of that session. */
                ctf_trace_try_destroy(session, ctf_trace);
        }
}

/*
 * Cleanup a session.
 */
static void cleanup_session(struct relay_connection *conn,
                struct relay_session *session)
{
        /*
         * Very important that this is done before destroying the session so we
         * can put back every viewer stream reference from the ctf_trace.
         */
        destroy_viewer_streams_by_session(session);
        try_destroy_streams(session);
        cds_list_del(&session->viewer_session_list);
        session_viewer_try_destroy(conn->sessions_ht, session);
}

/*
 * Send the viewer the list of current sessions.
 */
static
int viewer_get_new_streams(struct relay_connection *conn)
{
        int ret, send_streams = 0;
        uint32_t nb_created = 0, nb_unsent = 0, nb_streams = 0;
        struct lttng_viewer_new_streams_request request;
        struct lttng_viewer_new_streams_response response;
        struct relay_session *session;
        uint64_t session_id;

        assert(conn);

        DBG("Get new streams received");

        health_code_update();

        /* Receive the request from the connected client. */
        ret = recv_request(conn->sock, &request, sizeof(request));
        if (ret < 0) {
                goto error;
        }
        session_id = be64toh(request.session_id);

        health_code_update();

        memset(&response, 0, sizeof(response));

        rcu_read_lock();
        session = session_find_by_id(conn->sessions_ht, session_id);
        if (!session) {
                DBG("Relay session %" PRIu64 " not found", session_id);
                response.status = htobe32(LTTNG_VIEWER_NEW_STREAMS_ERR);
                goto send_reply;
        }

        if (!session_attached(conn, session_id)) {
                send_streams = 0;
                response.status = htobe32(LTTNG_VIEWER_NEW_STREAMS_ERR);
                goto send_reply;
        }

        send_streams = 1;
        response.status = htobe32(LTTNG_VIEWER_NEW_STREAMS_OK);

        ret = make_viewer_streams(session, LTTNG_VIEWER_SEEK_LAST, NULL, &nb_unsent,
                        &nb_created);
        if (ret < 0) {
                goto end_unlock;
        }
        /* Only send back the newly created streams with the unsent ones. */
        nb_streams = nb_created + nb_unsent;
        response.streams_count = htobe32(nb_streams);

        /*
         * If the session is closed and we have no new streams to send,
         * it means that the viewer has already received the whole trace
         * for this session and should now close it.
         */
        if (nb_streams == 0 && session->close_flag) {
                send_streams = 0;
                response.status = htobe32(LTTNG_VIEWER_NEW_STREAMS_HUP);
                /*
                 * Remove the session from the attached list of the connection
                 * and try to destroy it.
                 */
                cds_list_del(&session->viewer_session_list);
                cleanup_session(conn, session);
                goto send_reply;
        }

send_reply:
        health_code_update();
        ret = send_response(conn->sock, &response, sizeof(response));
        if (ret < 0) {
                goto end_unlock;
        }
        health_code_update();

        /*
         * Unknown or empty session, just return gracefully, the viewer knows what
         * is happening.
         */
        if (!send_streams || !nb_streams) {
                ret = 0;
                goto end_unlock;
        }

        /*
         * Send stream and *DON'T* ignore the sent flag so every viewer streams
         * that were not sent from that point will be sent to the viewer.
         */
        ret = send_viewer_streams(conn->sock, session, 0);
        if (ret < 0) {
                goto end_unlock;
        }

end_unlock:
        rcu_read_unlock();
error:
        return ret;
}

/*
 * Send the viewer the list of current sessions.
 */
static
int viewer_attach_session(struct relay_connection *conn)
{
        int send_streams = 0;
        ssize_t ret;
        uint32_t nb_streams = 0;
        enum lttng_viewer_seek seek_type;
        struct lttng_viewer_attach_session_request request;
        struct lttng_viewer_attach_session_response response;
        struct relay_session *session;

        assert(conn);

        health_code_update();

        /* Receive the request from the connected client. */
        ret = recv_request(conn->sock, &request, sizeof(request));
        if (ret < 0) {
                goto error;
        }

        health_code_update();

        memset(&response, 0, sizeof(response));

        if (!conn->viewer_session) {
                DBG("Client trying to attach before creating a live viewer session");
                response.status = htobe32(LTTNG_VIEWER_ATTACH_NO_SESSION);
                goto send_reply;
        }

        rcu_read_lock();
        session = session_find_by_id(conn->sessions_ht,
                        be64toh(request.session_id));
        if (!session) {
                DBG("Relay session %" PRIu64 " not found",
                                be64toh(request.session_id));
                response.status = htobe32(LTTNG_VIEWER_ATTACH_UNK);
                goto send_reply;
        }
        session_viewer_attach(session);
        DBG("Attach session ID %" PRIu64 " received", be64toh(request.session_id));

        if (uatomic_read(&session->viewer_refcount) > 1) {
                DBG("Already a viewer attached");
                response.status = htobe32(LTTNG_VIEWER_ATTACH_ALREADY);
                session_viewer_detach(session);
                goto send_reply;
        } else if (session->live_timer == 0) {
                DBG("Not live session");
                response.status = htobe32(LTTNG_VIEWER_ATTACH_NOT_LIVE);
                goto send_reply;
        } else {
                send_streams = 1;
                response.status = htobe32(LTTNG_VIEWER_ATTACH_OK);
                cds_list_add(&session->viewer_session_list,
                                &conn->viewer_session->sessions_head);
        }

        switch (be32toh(request.seek)) {
        case LTTNG_VIEWER_SEEK_BEGINNING:
        case LTTNG_VIEWER_SEEK_LAST:
                seek_type = be32toh(request.seek);
                break;
        default:
                ERR("Wrong seek parameter");
                response.status = htobe32(LTTNG_VIEWER_ATTACH_SEEK_ERR);
                send_streams = 0;
                goto send_reply;
        }

        ret = make_viewer_streams(session, seek_type, &nb_streams, NULL, NULL);
        if (ret < 0) {
                goto end_unlock;
        }
        response.streams_count = htobe32(nb_streams);

send_reply:
        health_code_update();
        ret = send_response(conn->sock, &response, sizeof(response));
        if (ret < 0) {
                goto end_unlock;
        }
        health_code_update();

        /*
         * Unknown or empty session, just return gracefully, the viewer knows what
         * is happening.
         */
        if (!send_streams || !nb_streams) {
                ret = 0;
                goto end_unlock;
        }

        /* Send stream and ignore the sent flag. */
        ret = send_viewer_streams(conn->sock, session, 1);
        if (ret < 0) {
                goto end_unlock;
        }

end_unlock:
        rcu_read_unlock();
error:
        return ret;
}

/*
 * Open the index file if needed for the given vstream.
 *
 * If an index file is successfully opened, the index_read_fd of the stream is
 * set with it.
 *
 * Return 0 on success, a negative value on error (-ENOENT if not ready yet).
 */
static int try_open_index(struct relay_viewer_stream *vstream,
                struct relay_stream *rstream)
{
        int ret = 0;

        assert(vstream);
        assert(rstream);

        if (vstream->index_read_fd >= 0) {
                goto end;
        }

        /*
         * First time, we open the index file and at least one index is ready.  The
         * race between the read and write of the total_index_received is
         * acceptable here since the client will be notified to simply come back
         * and get the next index.
         */
        if (rstream->total_index_received <= 0) {
                ret = -ENOENT;
                goto end;
        }
        ret = index_open(vstream->path_name, vstream->channel_name,
                        vstream->tracefile_count, vstream->tracefile_count_current);
        if (ret >= 0) {
                vstream->index_read_fd = ret;
                ret = 0;
                goto end;
        }

end:
        return ret;
}

/*
 * Check the status of the index for the given stream. This function updates
 * the index structure if needed and can destroy the vstream also for the HUP
 * situation.
 *
 * Return 0 means that we can proceed with the index. A value of 1 means that
 * the index has been updated and is ready to be send to the client. A negative
 * value indicates an error that can't be handled.
 */
static int check_index_status(struct relay_viewer_stream *vstream,
                struct relay_stream *rstream, struct ctf_trace *trace,
                struct lttng_viewer_index *index)
{
        int ret;

        assert(vstream);
        assert(rstream);
        assert(index);
        assert(trace);

        if (!rstream->close_flag) {
                /* Rotate on abort (overwrite). */
                if (vstream->abort_flag) {
                        DBG("Viewer stream %" PRIu64 " rotate because of overwrite",
                                        vstream->stream_handle);
                        ret = viewer_stream_rotate(vstream, rstream);
                        if (ret < 0) {
                                goto error;
                        } else if (ret == 1) {
                                /* EOF */
                                index->status = htobe32(LTTNG_VIEWER_INDEX_HUP);
                                goto hup;
                        }
                        /* ret == 0 means successful so we continue. */
                }

                /* Check if we are in the same trace file at this point. */
                if (rstream->tracefile_count_current == vstream->tracefile_count_current) {
                        if (rstream->beacon_ts_end != -1ULL &&
                                        vstream->last_sent_index == rstream->total_index_received) {
                                /*
                                 * We've received a synchronization beacon and the last index
                                 * available has been sent, the index for now is inactive.
                                 */
                                index->status = htobe32(LTTNG_VIEWER_INDEX_INACTIVE);
                                index->timestamp_end = htobe64(rstream->beacon_ts_end);
                                index->stream_id = htobe64(rstream->ctf_stream_id);
                                goto index_ready;
                        } else if (rstream->total_index_received <= vstream->last_sent_index
                                        && !vstream->close_write_flag) {
                                /*
                                 * Reader and writer are working in the same tracefile, so we care
                                 * about the number of index received and sent. Otherwise, we read
                                 * up to EOF.
                                 */
                                index->status = htobe32(LTTNG_VIEWER_INDEX_RETRY);
                                goto index_ready;
                        }
                }
                /* Nothing to do with the index, continue with it. */
                ret = 0;
        } else if (rstream->close_flag && vstream->close_write_flag &&
                        vstream->total_index_received == vstream->last_sent_index) {
                /* Last index sent and current tracefile closed in write */
                index->status = htobe32(LTTNG_VIEWER_INDEX_HUP);
                goto hup;
        } else {
                vstream->close_write_flag = 1;
                ret = 0;
        }

error:
        return ret;

hup:
        viewer_stream_delete(vstream);
        viewer_stream_destroy(trace, vstream);
index_ready:
        return 1;
}

/*
 * Send the next index for a stream.
 *
 * Return 0 on success or else a negative value.
 */
static
int viewer_get_next_index(struct relay_connection *conn)
{
        int ret;
        ssize_t read_ret;
        struct lttng_viewer_get_next_index request_index;
        struct lttng_viewer_index viewer_index;
        struct ctf_packet_index packet_index;
        struct relay_viewer_stream *vstream;
        struct relay_stream *rstream;
        struct ctf_trace *ctf_trace;
        struct relay_session *session;

        assert(conn);

        DBG("Viewer get next index");

        health_code_update();

        ret = recv_request(conn->sock, &request_index, sizeof(request_index));
        if (ret < 0) {
                goto end;
        }
        health_code_update();

        rcu_read_lock();
        vstream = viewer_stream_find_by_id(be64toh(request_index.stream_id));
        if (!vstream) {
                ret = -1;
                goto end_unlock;
        }

        session = session_find_by_id(conn->sessions_ht, vstream->session_id);
        if (!session) {
                ret = -1;
                goto end_unlock;
        }

        ctf_trace = ctf_trace_find_by_path(session->ctf_traces_ht, vstream->path_name);
        assert(ctf_trace);

        memset(&viewer_index, 0, sizeof(viewer_index));

        /*
         * The viewer should not ask for index on metadata stream.
         */
        if (vstream->metadata_flag) {
                viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_HUP);
                goto send_reply;
        }

        rstream = stream_find_by_id(relay_streams_ht, vstream->stream_handle);
        assert(rstream);

        /* Try to open an index if one is needed for that stream. */
        ret = try_open_index(vstream, rstream);
        if (ret < 0) {
                if (ret == -ENOENT) {
                        /*
                         * The index is created only when the first data packet arrives, it
                         * might not be ready at the beginning of the session
                         */
                        viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_RETRY);
                } else {
                        /* Unhandled error. */
                        viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_ERR);
                }
                goto send_reply;
        }

        pthread_mutex_lock(&rstream->viewer_stream_rotation_lock);
        ret = check_index_status(vstream, rstream, ctf_trace, &viewer_index);
        pthread_mutex_unlock(&rstream->viewer_stream_rotation_lock);
        if (ret < 0) {
                goto end_unlock;
        } else if (ret == 1) {
                /*
                 * This means the viewer index data structure has been populated by the
                 * check call thus we now send back the reply to the client.
                 */
                goto send_reply;
        }
        /* At this point, ret MUST be 0 thus we continue with the get. */
        assert(!ret);

        if (!ctf_trace->metadata_received ||
                        ctf_trace->metadata_received > ctf_trace->metadata_sent) {
                viewer_index.flags |= LTTNG_VIEWER_FLAG_NEW_METADATA;
        }

        ret = check_new_streams(conn);
        if (ret < 0) {
                goto end_unlock;
        } else if (ret == 1) {
                viewer_index.flags |= LTTNG_VIEWER_FLAG_NEW_STREAM;
        }

        pthread_mutex_lock(&rstream->viewer_stream_rotation_lock);
        pthread_mutex_lock(&vstream->overwrite_lock);
        if (vstream->abort_flag) {
                /* The file is being overwritten by the writer, we cannot use it. */
                pthread_mutex_unlock(&vstream->overwrite_lock);
                ret = viewer_stream_rotate(vstream, rstream);
                pthread_mutex_unlock(&rstream->viewer_stream_rotation_lock);
                if (ret < 0) {
                        goto end_unlock;
                } else if (ret == 1) {
                        viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_HUP);
                        viewer_stream_delete(vstream);
                        viewer_stream_destroy(ctf_trace, vstream);
                } else {
                        viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_RETRY);
                }
                goto send_reply;
        }

        read_ret = lttng_read(vstream->index_read_fd, &packet_index,
                        sizeof(packet_index));
        pthread_mutex_unlock(&vstream->overwrite_lock);
        pthread_mutex_unlock(&rstream->viewer_stream_rotation_lock);
        if (read_ret < 0) {
                viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_HUP);
                viewer_stream_delete(vstream);
                viewer_stream_destroy(ctf_trace, vstream);
                goto send_reply;
        } else if (read_ret < sizeof(packet_index)) {
                pthread_mutex_lock(&rstream->viewer_stream_rotation_lock);
                if (vstream->close_write_flag) {
                        ret = viewer_stream_rotate(vstream, rstream);
                        if (ret < 0) {
                                pthread_mutex_unlock(&rstream->viewer_stream_rotation_lock);
                                goto end_unlock;
                        } else if (ret == 1) {
                                viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_HUP);
                                viewer_stream_delete(vstream);
                                viewer_stream_destroy(ctf_trace, vstream);
                        } else {
                                viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_RETRY);
                        }
                } else {
                        ERR("Relay reading index file %d", vstream->index_read_fd);
                        viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_ERR);
                }
                pthread_mutex_unlock(&rstream->viewer_stream_rotation_lock);
                goto send_reply;
        } else {
                viewer_index.status = htobe32(LTTNG_VIEWER_INDEX_OK);
                vstream->last_sent_index++;
        }

        /*
         * Indexes are stored in big endian, no need to switch before sending.
         */
        viewer_index.offset = packet_index.offset;
        viewer_index.packet_size = packet_index.packet_size;
        viewer_index.content_size = packet_index.content_size;
        viewer_index.timestamp_begin = packet_index.timestamp_begin;
        viewer_index.timestamp_end = packet_index.timestamp_end;
        viewer_index.events_discarded = packet_index.events_discarded;
        viewer_index.stream_id = packet_index.stream_id;

send_reply:
        viewer_index.flags = htobe32(viewer_index.flags);
        health_code_update();

        ret = send_response(conn->sock, &viewer_index, sizeof(viewer_index));
        if (ret < 0) {
                goto end_unlock;
        }
        health_code_update();

        DBG("Index %" PRIu64 " for stream %" PRIu64 " sent",
                        vstream->last_sent_index, vstream->stream_handle);

end_unlock:
        rcu_read_unlock();

end:
        return ret;
}

/*
 * Send the next index for a stream
 *
 * Return 0 on success or else a negative value.
 */
static
int viewer_get_packet(struct relay_connection *conn)
{
        int ret, send_data = 0;
        char *data = NULL;
        uint32_t len = 0;
        ssize_t read_len;
        struct lttng_viewer_get_packet get_packet_info;
        struct lttng_viewer_trace_packet reply;
        struct relay_viewer_stream *stream;
        struct relay_session *session;
        struct ctf_trace *ctf_trace;

        assert(conn);

        DBG2("Relay get data packet");

        health_code_update();

        ret = recv_request(conn->sock, &get_packet_info, sizeof(get_packet_info));
        if (ret < 0) {
                goto end;
        }
        health_code_update();

        /* From this point on, the error label can be reached. */
        memset(&reply, 0, sizeof(reply));

        rcu_read_lock();
        stream = viewer_stream_find_by_id(be64toh(get_packet_info.stream_id));
        if (!stream) {
                goto error;
        }

        session = session_find_by_id(conn->sessions_ht, stream->session_id);
        if (!session) {
                ret = -1;
                goto error;
        }

        ctf_trace = ctf_trace_find_by_path(session->ctf_traces_ht,
                        stream->path_name);
        assert(ctf_trace);

        /*
         * First time we read this stream, we need open the tracefile, we should
         * only arrive here if an index has already been sent to the viewer, so the
         * tracefile must exist, if it does not it is a fatal error.
         */
        if (stream->read_fd < 0) {
                char fullpath[PATH_MAX];

                if (stream->tracefile_count > 0) {
                        ret = snprintf(fullpath, PATH_MAX, "%s/%s_%" PRIu64, stream->path_name,
                                        stream->channel_name,
                                        stream->tracefile_count_current);
                } else {
                        ret = snprintf(fullpath, PATH_MAX, "%s/%s", stream->path_name,
                                        stream->channel_name);
                }
                if (ret < 0) {
                        goto error;
                }
                ret = open(fullpath, O_RDONLY);
                if (ret < 0) {
                        PERROR("Relay opening trace file");
                        goto error;
                }
                stream->read_fd = ret;
        }

        if (!ctf_trace->metadata_received ||
                        ctf_trace->metadata_received > ctf_trace->metadata_sent) {
                reply.status = htobe32(LTTNG_VIEWER_GET_PACKET_ERR);
                reply.flags |= LTTNG_VIEWER_FLAG_NEW_METADATA;
                goto send_reply;
        }

        ret = check_new_streams(conn);
        if (ret < 0) {
                goto end_unlock;
        } else if (ret == 1) {
                reply.status = htobe32(LTTNG_VIEWER_GET_PACKET_ERR);
                reply.flags |= LTTNG_VIEWER_FLAG_NEW_STREAM;
                goto send_reply;
        }

        len = be32toh(get_packet_info.len);
        data = zmalloc(len);
        if (!data) {
                PERROR("relay data zmalloc");
                goto error;
        }

        ret = lseek(stream->read_fd, be64toh(get_packet_info.offset), SEEK_SET);
        if (ret < 0) {
                /*
                 * If the read fd was closed by the streaming side, the
                 * abort_flag will be set to 1, otherwise it is an error.
                 */
                if (stream->abort_flag == 0) {
                        PERROR("lseek");
                        goto error;
                }
                reply.status = htobe32(LTTNG_VIEWER_GET_PACKET_EOF);
                goto send_reply;
        }
        read_len = lttng_read(stream->read_fd, data, len);
        if (read_len < len) {
                /*
                 * If the read fd was closed by the streaming side, the
                 * abort_flag will be set to 1, otherwise it is an error.
                 */
                if (stream->abort_flag == 0) {
                        PERROR("Relay reading trace file, fd: %d, offset: %" PRIu64,
                                        stream->read_fd,
                                        be64toh(get_packet_info.offset));
                        goto error;
                } else {
                        reply.status = htobe32(LTTNG_VIEWER_GET_PACKET_EOF);
                        goto send_reply;
                }
        }
        reply.status = htobe32(LTTNG_VIEWER_GET_PACKET_OK);
        reply.len = htobe32(len);
        send_data = 1;
        goto send_reply;

error:
        reply.status = htobe32(LTTNG_VIEWER_GET_PACKET_ERR);

send_reply:
        reply.flags = htobe32(reply.flags);

        health_code_update();

        ret = send_response(conn->sock, &reply, sizeof(reply));
        if (ret < 0) {
                goto end_unlock;
        }
        health_code_update();

        if (send_data) {
                health_code_update();
                ret = send_response(conn->sock, data, len);
                if (ret < 0) {
                        goto end_unlock;
                }
                health_code_update();
        }

        DBG("Sent %u bytes for stream %" PRIu64, len,
                        be64toh(get_packet_info.stream_id));

end_unlock:
        free(data);
        rcu_read_unlock();

end:
        return ret;
}

/*
 * Send the session's metadata
 *
 * Return 0 on success else a negative value.
 */
static
int viewer_get_metadata(struct relay_connection *conn)
{
        int ret = 0;
        ssize_t read_len;
        uint64_t len = 0;
        char *data = NULL;
        struct lttng_viewer_get_metadata request;
        struct lttng_viewer_metadata_packet reply;
        struct relay_viewer_stream *stream;
        struct ctf_trace *ctf_trace;
        struct relay_session *session;

        assert(conn);

        DBG("Relay get metadata");

        health_code_update();

        ret = recv_request(conn->sock, &request, sizeof(request));
        if (ret < 0) {
                goto end;
        }
        health_code_update();

        memset(&reply, 0, sizeof(reply));

        rcu_read_lock();
        stream = viewer_stream_find_by_id(be64toh(request.stream_id));
        if (!stream || !stream->metadata_flag) {
                ERR("Invalid metadata stream");
                goto error;
        }

        session = session_find_by_id(conn->sessions_ht, stream->session_id);
        if (!session) {
                ret = -1;
                goto error;
        }

        ctf_trace = ctf_trace_find_by_path(session->ctf_traces_ht,
                        stream->path_name);
        assert(ctf_trace);
        assert(ctf_trace->metadata_sent <= ctf_trace->metadata_received);

        len = ctf_trace->metadata_received - ctf_trace->metadata_sent;
        if (len == 0) {
                reply.status = htobe32(LTTNG_VIEWER_NO_NEW_METADATA);
                goto send_reply;
        }

        /* first time, we open the metadata file */
        if (stream->read_fd < 0) {
                char fullpath[PATH_MAX];

                ret = snprintf(fullpath, PATH_MAX, "%s/%s", stream->path_name,
                                stream->channel_name);
                if (ret < 0) {
                        goto error;
                }
                ret = open(fullpath, O_RDONLY);
                if (ret < 0) {
                        PERROR("Relay opening metadata file");
                        goto error;
                }
                stream->read_fd = ret;
        }

        reply.len = htobe64(len);
        data = zmalloc(len);
        if (!data) {
                PERROR("viewer metadata zmalloc");
                goto error;
        }

        read_len = lttng_read(stream->read_fd, data, len);
        if (read_len < len) {
                PERROR("Relay reading metadata file");
                goto error;
        }
        ctf_trace->metadata_sent += read_len;
        reply.status = htobe32(LTTNG_VIEWER_METADATA_OK);
        goto send_reply;

error:
        reply.status = htobe32(LTTNG_VIEWER_METADATA_ERR);

send_reply:
        health_code_update();
        ret = send_response(conn->sock, &reply, sizeof(reply));
        if (ret < 0) {
                goto end_unlock;
        }
        health_code_update();

        if (len > 0) {
                ret = send_response(conn->sock, data, len);
                if (ret < 0) {
                        goto end_unlock;
                }
        }

        DBG("Sent %" PRIu64 " bytes of metadata for stream %" PRIu64, len,
                        be64toh(request.stream_id));

        DBG("Metadata sent");

end_unlock:
        free(data);
        rcu_read_unlock();
end:
        return ret;
}

/*
 * Create a viewer session.
 *
 * Return 0 on success or else a negative value.
 */
static
int viewer_create_session(struct relay_connection *conn)
{
        int ret;
        struct lttng_viewer_create_session_response resp;

        DBG("Viewer create session received");

        memset(&resp, 0, sizeof(resp));
        resp.status = htobe32(LTTNG_VIEWER_CREATE_SESSION_OK);
        conn->viewer_session = zmalloc(sizeof(*conn->viewer_session));
        if (!conn->viewer_session) {
                ERR("Allocation viewer session");
                resp.status = htobe32(LTTNG_VIEWER_CREATE_SESSION_ERR);
                goto send_reply;
        }
        CDS_INIT_LIST_HEAD(&conn->viewer_session->sessions_head);

send_reply:
        health_code_update();
        ret = send_response(conn->sock, &resp, sizeof(resp));
        if (ret < 0) {
                goto end;
        }
        health_code_update();
        ret = 0;

end:
        return ret;
}


/*
 * live_relay_unknown_command: send -1 if received unknown command
 */
static
void live_relay_unknown_command(struct relay_connection *conn)
{
        struct lttcomm_relayd_generic_reply reply;

        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(LTTNG_ERR_UNK);
        (void) send_response(conn->sock, &reply, sizeof(reply));
}

/*
 * Process the commands received on the control socket
 */
static
int process_control(struct lttng_viewer_cmd *recv_hdr,
                struct relay_connection *conn)
{
        int ret = 0;
        uint32_t msg_value;

        assert(recv_hdr);
        assert(conn);

        msg_value = be32toh(recv_hdr->cmd);

        /*
         * Make sure we've done the version check before any command other then a
         * new client connection.
         */
        if (msg_value != LTTNG_VIEWER_CONNECT && !conn->version_check_done) {
                ERR("Viewer conn value %" PRIu32 " before version check", msg_value);
                ret = -1;
                goto end;
        }

        switch (msg_value) {
        case LTTNG_VIEWER_CONNECT:
                ret = viewer_connect(conn);
                break;
        case LTTNG_VIEWER_LIST_SESSIONS:
                ret = viewer_list_sessions(conn);
                break;
        case LTTNG_VIEWER_ATTACH_SESSION:
                ret = viewer_attach_session(conn);
                break;
        case LTTNG_VIEWER_GET_NEXT_INDEX:
                ret = viewer_get_next_index(conn);
                break;
        case LTTNG_VIEWER_GET_PACKET:
                ret = viewer_get_packet(conn);
                break;
        case LTTNG_VIEWER_GET_METADATA:
                ret = viewer_get_metadata(conn);
                break;
        case LTTNG_VIEWER_GET_NEW_STREAMS:
                ret = viewer_get_new_streams(conn);
                break;
        case LTTNG_VIEWER_CREATE_SESSION:
                ret = viewer_create_session(conn);
                break;
        default:
                ERR("Received unknown viewer command (%u)", be32toh(recv_hdr->cmd));
                live_relay_unknown_command(conn);
                ret = -1;
                goto end;
        }

end:
        return ret;
}

static
void cleanup_connection_pollfd(struct lttng_poll_event *events, int pollfd)
{
        int ret;

        assert(events);

        (void) lttng_poll_del(events, pollfd);

        ret = close(pollfd);
        if (ret < 0) {
                ERR("Closing pollfd %d", pollfd);
        }
}

/*
 * Delete and destroy a connection.
 *
 * RCU read side lock MUST be acquired.
 */
static void destroy_connection(struct lttng_ht *relay_connections_ht,
                struct relay_connection *conn)
{
        struct relay_session *session, *tmp_session;

        assert(relay_connections_ht);
        assert(conn);

        connection_delete(relay_connections_ht, conn);

        if (!conn->viewer_session) {
                goto end;
        }

        rcu_read_lock();
        cds_list_for_each_entry_safe(session, tmp_session,
                        &conn->viewer_session->sessions_head,
                        viewer_session_list) {
                DBG("Cleaning connection of session ID %" PRIu64, session->id);
                cleanup_session(conn, session);
        }
        rcu_read_unlock();

end:
        connection_destroy(conn);
}

/*
 * This thread does the actual work
 */
static
void *thread_worker(void *data)
{
        int ret, err = -1;
        uint32_t nb_fd;
        struct relay_connection *conn;
        struct lttng_poll_event events;
        struct lttng_ht *relay_connections_ht;
        struct lttng_ht_iter iter;
        struct lttng_viewer_cmd recv_hdr;
        struct relay_local_data *relay_ctx = (struct relay_local_data *) data;
        struct lttng_ht *sessions_ht = relay_ctx->sessions_ht;

        DBG("[thread] Live viewer relay worker started");

        rcu_register_thread();

        health_register(health_relayd, HEALTH_RELAYD_TYPE_LIVE_WORKER);

        if (testpoint(relayd_thread_live_worker)) {
                goto error_testpoint;
        }

        /* table of connections indexed on socket */
        relay_connections_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
        if (!relay_connections_ht) {
                goto relay_connections_ht_error;
        }

        ret = create_thread_poll_set(&events, 2);
        if (ret < 0) {
                goto error_poll_create;
        }

        ret = lttng_poll_add(&events, live_conn_pipe[0], LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
        }

restart:
        while (1) {
                int i;

                health_code_update();

                /* Infinite blocking call, waiting for transmission */
                DBG3("Relayd live viewer worker thread polling...");
                health_poll_entry();
                ret = lttng_poll_wait(&events, -1);
                health_poll_exit();
                if (ret < 0) {
                        /*
                         * Restart interrupted system call.
                         */
                        if (errno == EINTR) {
                                goto restart;
                        }
                        goto error;
                }

                nb_fd = ret;

                /*
                 * Process control. The control connection is prioritised so we don't
                 * starve it with high throughput tracing data on the data
                 * connection.
                 */
                for (i = 0; i < nb_fd; i++) {
                        /* Fetch once the poll data */
                        uint32_t revents = LTTNG_POLL_GETEV(&events, i);
                        int pollfd = LTTNG_POLL_GETFD(&events, i);

                        health_code_update();

                        if (!revents) {
                                /* No activity for this FD (poll implementation). */
                                continue;
                        }

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                err = 0;
                                goto exit;
                        }

                        /* Inspect the relay conn pipe for new connection */
                        if (pollfd == live_conn_pipe[0]) {
                                if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                        ERR("Relay live pipe error");
                                        goto error;
                                } else if (revents & LPOLLIN) {
                                        ret = lttng_read(live_conn_pipe[0], &conn, sizeof(conn));
                                        if (ret < 0) {
                                                goto error;
                                        }
                                        conn->sessions_ht = sessions_ht;
                                        connection_init(conn);
                                        lttng_poll_add(&events, conn->sock->fd,
                                                        LPOLLIN | LPOLLRDHUP);
                                        rcu_read_lock();
                                        lttng_ht_add_unique_ulong(relay_connections_ht,
                                                        &conn->sock_n);
                                        rcu_read_unlock();
                                        DBG("Connection socket %d added", conn->sock->fd);
                                }
                        } else {
                                rcu_read_lock();
                                conn = connection_find_by_sock(relay_connections_ht, pollfd);
                                /* If not found, there is a synchronization issue. */
                                assert(conn);

                                if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                        cleanup_connection_pollfd(&events, pollfd);
                                        destroy_connection(relay_connections_ht, conn);
                                } else if (revents & LPOLLIN) {
                                        ret = conn->sock->ops->recvmsg(conn->sock, &recv_hdr,
                                                        sizeof(recv_hdr), 0);
                                        if (ret <= 0) {
                                                /* Connection closed */
                                                cleanup_connection_pollfd(&events, pollfd);
                                                destroy_connection(relay_connections_ht, conn);
                                                DBG("Viewer control conn closed with %d", pollfd);
                                        } else {
                                                ret = process_control(&recv_hdr, conn);
                                                if (ret < 0) {
                                                        /* Clear the session on error. */
                                                        cleanup_connection_pollfd(&events, pollfd);
                                                        destroy_connection(relay_connections_ht, conn);
                                                        DBG("Viewer connection closed with %d", pollfd);
                                                }
                                        }
                                }
                                rcu_read_unlock();
                        }
                }
        }

exit:
error:
        lttng_poll_clean(&events);

        /* Cleanup reamaining connection object. */
        rcu_read_lock();
        cds_lfht_for_each_entry(relay_connections_ht->ht, &iter.iter, conn,
                        sock_n.node) {
                health_code_update();
                destroy_connection(relay_connections_ht, conn);
        }
        rcu_read_unlock();
error_poll_create:
        lttng_ht_destroy(relay_connections_ht);
relay_connections_ht_error:
        /* Close relay conn pipes */
        utils_close_pipe(live_conn_pipe);
        if (err) {
                DBG("Viewer worker thread exited with error");
        }
        DBG("Viewer worker thread cleanup complete");
error_testpoint:
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }
        health_unregister(health_relayd);
        stop_threads();
        rcu_unregister_thread();
        return NULL;
}

/*
 * Create the relay command pipe to wake thread_manage_apps.
 * Closed in cleanup().
 */
static int create_conn_pipe(void)
{
        int ret;

        ret = utils_create_pipe_cloexec(live_conn_pipe);

        return ret;
}

void live_stop_threads(void)
{
        int ret;
        void *status;

        stop_threads();

        ret = pthread_join(live_listener_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join live listener");
                goto error;     /* join error, exit without cleanup */
        }

        ret = pthread_join(live_worker_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join live worker");
                goto error;     /* join error, exit without cleanup */
        }

        ret = pthread_join(live_dispatcher_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join live dispatcher");
                goto error;     /* join error, exit without cleanup */
        }

        cleanup();

error:
        return;
}

/*
 * main
 */
int live_start_threads(struct lttng_uri *uri,
                struct relay_local_data *relay_ctx)
{
        int ret = 0;
        void *status;
        int is_root;

        assert(uri);
        live_uri = uri;

        /* Check if daemon is UID = 0 */
        is_root = !getuid();

        if (!is_root) {
                if (live_uri->port < 1024) {
                        ERR("Need to be root to use ports < 1024");
                        ret = -1;
                        goto exit;
                }
        }

        /* Setup the thread apps communication pipe. */
        if ((ret = create_conn_pipe()) < 0) {
                goto exit;
        }

        /* Init relay command queue. */
        cds_wfcq_init(&viewer_conn_queue.head, &viewer_conn_queue.tail);

        /* Set up max poll set size */
        lttng_poll_set_max_size();

        /* Setup the dispatcher thread */
        ret = pthread_create(&live_dispatcher_thread, NULL,
                        thread_dispatcher, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create viewer dispatcher");
                goto exit_dispatcher;
        }

        /* Setup the worker thread */
        ret = pthread_create(&live_worker_thread, NULL,
                        thread_worker, relay_ctx);
        if (ret != 0) {
                PERROR("pthread_create viewer worker");
                goto exit_worker;
        }

        /* Setup the listener thread */
        ret = pthread_create(&live_listener_thread, NULL,
                        thread_listener, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create viewer listener");
                goto exit_listener;
        }

        ret = 0;
        goto end;

exit_listener:
        ret = pthread_join(live_listener_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join live listener");
                goto error;     /* join error, exit without cleanup */
        }

exit_worker:
        ret = pthread_join(live_worker_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join live worker");
                goto error;     /* join error, exit without cleanup */
        }

exit_dispatcher:
        ret = pthread_join(live_dispatcher_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join live dispatcher");
                goto error;     /* join error, exit without cleanup */
        }

exit:
        cleanup();

end:
error:
        return ret;
}